diff --git a/src/secp256k1/.travis.yml b/src/secp256k1/.travis.yml
--- a/src/secp256k1/.travis.yml
+++ b/src/secp256k1/.travis.yml
@@ -64,6 +64,9 @@
     - AUTOTOOLS_EXTRA_FLAGS=CPPFLAGS=-DDETERMINISTIC CMAKE_EXTRA_FLAGS=-DCMAKE_C_FLAGS=-DDETERMINISTIC
     - AUTOTOOLS_EXTRA_FLAGS=CFLAGS=-O0               CMAKE_EXTRA_FLAGS=-DCMAKE_BUILD_TYPE=Debug CTIMETEST=no
     - AUTOTOOLS_TARGET=check-java      CMAKE_TARGET=check-secp256k1-java JNI=yes ECDH=yes EXPERIMENTAL=yes WITH_VALGRIND=no CTIMETEST=no BENCH=no
+    - CFLAGS="-fsanitize=undefined -fno-omit-frame-pointer" LDFLAGS="-fsanitize=undefined -fno-omit-frame-pointer"
+      UBSAN_OPTIONS="print_stacktrace=1:halt_on_error=1"
+      BIGNUM=no ASM=x86_64 ECDH=yes RECOVERY=yes EXPERIMENTAL=yes MULTISET=yes SCHNORRSIG=yes CTIMETEST=no
     - ECMULTGENPRECISION=2
     - ECMULTGENPRECISION=8
     - RUN_VALGRIND=yes
diff --git a/src/secp256k1/src/ecmult_impl.h b/src/secp256k1/src/ecmult_impl.h
--- a/src/secp256k1/src/ecmult_impl.h
+++ b/src/secp256k1/src/ecmult_impl.h
@@ -595,11 +595,11 @@
     scalars = (secp256k1_scalar*)secp256k1_scratch_alloc(error_callback, scratch, n_points * sizeof(secp256k1_scalar));
     state.prej = (secp256k1_gej*)secp256k1_scratch_alloc(error_callback, scratch, n_points * ECMULT_TABLE_SIZE(WINDOW_A) * sizeof(secp256k1_gej));
     state.zr = (secp256k1_fe*)secp256k1_scratch_alloc(error_callback, scratch, n_points * ECMULT_TABLE_SIZE(WINDOW_A) * sizeof(secp256k1_fe));
-    state.pre_a = (secp256k1_ge*)secp256k1_scratch_alloc(error_callback, scratch, n_points * 2 * ECMULT_TABLE_SIZE(WINDOW_A) * sizeof(secp256k1_ge));
-    state.pre_a_lam = state.pre_a + n_points * ECMULT_TABLE_SIZE(WINDOW_A);
+    state.pre_a = (secp256k1_ge*)secp256k1_scratch_alloc(error_callback, scratch, n_points * ECMULT_TABLE_SIZE(WINDOW_A) * sizeof(secp256k1_ge));
+    state.pre_a_lam = (secp256k1_ge*)secp256k1_scratch_alloc(error_callback, scratch, n_points * ECMULT_TABLE_SIZE(WINDOW_A) * sizeof(secp256k1_ge));
     state.ps = (struct secp256k1_strauss_point_state*)secp256k1_scratch_alloc(error_callback, scratch, n_points * sizeof(struct secp256k1_strauss_point_state));
 
-    if (points == NULL || scalars == NULL || state.prej == NULL || state.zr == NULL || state.pre_a == NULL) {
+    if (points == NULL || scalars == NULL || state.prej == NULL || state.zr == NULL || state.pre_a == NULL || state.pre_a_lam == NULL || state.ps == NULL) {
         secp256k1_scratch_apply_checkpoint(error_callback, scratch, scratch_checkpoint);
         return 0;
     }